31.3 Chapter 4

31.3.1 problem 2
31.3.2 problem 4
31.3.3 problem 5.1
31.3.4 problem 5.2
31.3.5 problem 5.3
31.3.6 problem 5.4
31.3.7 problem 5.4
31.3.8 problem 7.1
31.3.9 problem 7.1